This invention relates to anti-dandruff shampoos containing a preservative. In particular, it relates to the use of zinc compounds to stabilize the activity of a thiazolinone preservative added to an anti-dandruff shampoo containing zinc pyrithione.
It is known that microbiological contamination can result in poor shelf life and aesthetics of shampoos. Accordingly, preservatives are usually added to the shampoo composition during the manufacture of the shampoo to reduce or eliminate such contamination. One problem with adding a preservative to an anti-dandruff shampoo is that other ingredients present in the shampoo may react adversely with the preservative and reduce its activity. Specifically, it has been found that zinc pyrithione reacts adversely with some thiazolinone preservatives to reduce its activity and in turn its ability to prevent or reduce microbiological contamination.
Consequently, there is a need for an anti-dandruff shampoo having a stable active preservative. Surprisingly, it has been found that the activity of a thiazolinone preservative in an zinc pyrithione shampoo can be maintained by adding a stabilizer comprising a zinc compound.
The present invention thus provides a zinc pyrithione anti-dandruff shampoo having stable thiazolinone preservative.